> [!CAUTION]
> **Caution:** This documentation is for Google Ads API **v23** . The latest active version is [**v26**](https://developers.google.com/google-ads/api/reference/rpc/latest/BidModifierSourceEnum.BidModifierSource).

Enum describing possible bid modifier sources.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v23/enums/bid_modifier_source.proto)

| Enums ||
|---|---|
| ## `AD_GROUP` | The bid modifier is specified (overridden) at the ad group level. |
| ## `CAMPAIGN` | The bid modifier is specified at the campaign level, on the campaign level criterion. |
| ## `UNKNOWN` | Used for return value only. Represents value unknown in this version. |
| ## `UNSPECIFIED` | Not specified. |